This thread is getting started to explore tube types, different numbers, that can be used in the Seduction (and now Reduction) without any circuit modifications. That is, drop in equivalents.
These are the ones I have found. I will modify the OP with others as posters contribute other numbers.
If anyone finds that I have a tube with the wrong pin out, or higher heater current than the Seduction can supply please post and I will modify the OP accordingly.
Seduction Tube Equivalents (in numerical order):
6DJ8
6DJ8 (just the generic, many below are better spec tubes)
6N23P (P9 is shield) -EV are tighter specs
CV2492
CV2493
CV4108
CV4109
CV4110
CV5231
CV5354
CV5358
ECC88
E188C
E188CC
E288CC ?
E88CC
6922
7308
Edit: Three dropped.